Time-domain multiplexing of power and data

ABSTRACT

Circuits, methods, and apparatus that may allow an electronic device to control a power adapter. One example may provide an electronic system where an electronic device may control a power adapter through a communication channel. Data transferred in the communication channel may include the temperature of the power adapter, the charging capability of the adapter, and other types of data. In one example, power and data may share the same two wires, and the power and data may be time-division multiplexed. That is, the two wires may convey power and data at different times. Another example may include circuitry to detect a connection between the electronic device and the power adapter. Once a connection is detected, power may be transferred from the power adapter to the electronic device. This power transfer may be interrupted on occasion to transfer data between the power adapter to the electronic device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/286,982, filed Nov. 1, 2011, which claims the benefit of U.S.provisional patent application No. 61/482,195, filed May 3, 2011, whichare incorporated by reference.

BACKGROUND

The number and types of electronic devices available to consumers hasincreased tremendously the past few years, and that rate of increaseshows no signs of abating any time soon. These electronic devicesinclude portable devices, such as laptop, netbook, or tablet computers,cell, media, or smart phones, global positioning devices, media players,and other such devices.

These portable devices need to be supplied power during operation, andthis power may come from external sources or internal sources, such asbatteries. These batteries typically need to be charged using anexternal source, such as a power adapter. These power adapters mayreceive AC power from a wall outlet, car charger, or other source, andprovide DC power that may be used to charge batteries.

But some devices, such as laptop computers, are very computationallypowerful, and therefore require a fair amount of power. Complicatingthis further is the fact that users of these laptops want to be able torun their laptops for extended periods of time without having torecharge the batteries. Moreover, when a user does connect to a powersource to charge the batteries, it is likely the user wants to have thebatteries charge very quickly so that the user is free to disconnectfrom the power source.

For these reasons, many newer electronic devices have relatively largebatteries. Accordingly, it has become desirable to be able to providelarge amounts of charging power very quickly.

But this quick charging is not without its drawbacks. For example, thisquick charging may cause high temperatures in a power adapter. To coolthe power adapter, the power adapter may need to be made fairly large,such that heat may be dissipated. To avoid this, it may be desirable foran electronic device to control or adjust the power adapter in order tomaintain the temperature of the power adapter.

Thus, what is needed are circuits, methods, and apparatus that allow anelectronic device to control a power adapter.

SUMMARY

Accordingly, embodiments of the present invention provide circuits,methods, and apparatus that allow an electronic device to control apower adapter. In various embodiments of the present invention, this mayallow the electronic device to control the power the electronic devicereceives.

An illustrative embodiment of the present invention may provide anelectronic system where an electronic device may control a power adapterthrough a communication channel. That is, the electronic device maycontrol the power adapter by sending data to the power adapter, andreceiving data from the power adapter.

In various embodiments of the present invention, various types of datamay be transmitted. This data may include the temperature of the poweradapter, the charging capability of the adapter, and other types ofdata. The electronic device may use this data to adjust the currentdrawn from the power adapter, and thereby control the power adaptertemperature. This may allow the use of smaller, less expensive, poweradapters.

This data may also include a command provided by the electronic deviceto the power adapter to turn the power adapter off. This is particularlyuseful when it is more power efficient for a battery in the electronicdevice to provide power to the electronic device than it is for theelectronic device to receive its power from the power adapter.

In other embodiments of the present invention, other types of data maybe transmitted. For example, identification data that includes currentand voltage capabilities, adapter identification, or version informationmay be transmitted. Still other embodiments of the present invention mayinclude fault logging. Faults, such as overheating, overvoltage, or overcurrent faults may be transmitted or stored by either or both theelectronic device and the power adapter.

In some embodiments of the present invention, the electronic devicebeing charged may act as a master device, while the power adapter mayact as a slave device. In other embodiments of the present invention,the electronic device being charged may act as a slave device, while thepower adapter may act as a master device. In still other embodiments ofthe present invention, the electronic device and the power adapter maytransfer data as peers, that is, in a peer-to-peer configuration.

In various embodiments of the present invention, data may be transmittedand received over the same two conductors that provide power and groundto the electronic device. In other embodiments of the present invention,one, two, or more than two additional wires may be provided for thiscommunication. Using the same conductors to provide power and datareduces the amount of wires in a cable from the power adapter and allowsa cable of a given size to provide a maximum amount of power for itssize.

In embodiments of the present invention where power and data share thesame two wires, power and data may be multiplexed in various ways. Forexample, power and data may be frequency multiplexed. In an illustrativeembodiment of the present invention, large filters that may be requiredfor frequency multiplexing are avoided and time division multiplexingmay be used. That is, the two wires may convey power and data atdifferent times.

An illustrative embodiment of the present invention may includecircuitry to detect a connection between the electronic device and thepower adapter. Once a connection is detected, power may be transferredfrom the power adapter to the electronic device. This power transfer maybe interrupted on occasion to transfer data between the power adapterand the electronic device.

This detection circuit may include circuits in a power adapter and anelectronic device. The power adapter detection circuitry may include avoltage supply coupled to a detect resistor that is in series with acable conductor. When the cable is connected to the electronic device, asystem identification resistor may draw current from the power adaptervoltage supply, thereby generating a voltage on the cable conductor. Thevoltage on the cable conductor may be detected, for example, by using ananalog-to-digital converter.

The value of the voltage on the cable conductor may be used to determinethe value of the system resistor, which may indicate information aboutthe electronic device. For example, the voltage may simply indicate thata connection has been made to the electronic device. In otherembodiments of the present invention, other information, such as thetype of electronic device, the charge or voltage that may be accepted bythe electronic device, or other aspect of the electronic device may beconveyed by the value of system resistor and resultant voltage on thecable conductor.

In other embodiments of the present invention, other detect circuitrymay be employed by the power adapter. For example, in a specificembodiment of the present invention, a second resistor may be switchedin parallel (or series) with the detect resistor in the power adapter.This second resistor may be switched in and a second resultant voltageon the cable conductor measured. This technique may provide two voltagesthat can be subtracted from each other to generate a differentialmeasurement. This differential measurement may have a reducedsensitivity to component leakage, diode drops, and other circuiteffects. In other embodiments of the present invention, the voltagesupply used during detection may be varied.

In still other embodiments of the present invention, other systemidentification circuitry may be employed by the electronic device. In aspecific embodiment of the present invention, a first resistor inparallel with a series combination of a second resistor and a diode maybe used. When a low voltage is received at the electronic device, thediode may be off, and the load may appear to be the first resistor. Thisresistor may be used to indicate that a connection to an electronicdevice has been made by the power adapter. As the received voltage isincreased, the diode may turn on, and the load may appear to be(approximately) the first and second resistors in parallel. Theinclusion of this second resistor may be used to verify the connection.In other embodiments of the present invention, the value of the secondresistor may convey other information about the electronic device, asdescribed above.

In another specific embodiment of the present invention, a firstresistor in parallel with a diode may be used. When a high voltage isreceived at the electronic device, the diode may clamp the voltage. Asthe received voltage is lowered, the diode may turn off, and the loadmay appear as the first resistor. Again, this two-step process may beused to verify a connection between a power adapter and an electronicdevice. In other embodiments the present invention, the first resistorvalue may convey other information about the electronic device, asdescribed above.

These power adapters typically are connected through a cable to aconnector insert. This connector insert may have a first form factor. Onoccasion, it may be desirable to connect such a power adapter to alegacy or other electronic device that may house a connector receptaclearranged to accept connector inserts having a second form factor.Accordingly, embodiments of the present invention may provide aconverter or connector adapter having a connector receptacle to accept aconnector insert having the first form factor. The converter may furtherinclude a connector insert having the second form factor. This connectoradapter may further include circuitry such that the adapter may bedetected by a power adapter. This connector adapter may includecircuitry to provide a power connection from its connector receptacle toits connector insert. In a specific embodiment of the present invention,a resistor may be coupled between the connector receptacle and connectorinsert. A switch, such as a field effect transistor, may be coupledacross the resistor and controlled by control circuitry. The resistormay have a value that is detected by power adapter, which may identifythe resistor be a value associated with a converter or connectoradapter. After detection, as power is applied by the power adapter,control circuitry may activate the switch, thereby shorting the resistorand providing power through the converter to the electronic device.

Various embodiments of the present invention may incorporate one or moreof these and the other features described herein. A better understandingof the nature and advantages of the present invention may be gained byreference to the following detailed description and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an electronic system that may be improved by theincorporation of embodiments of the present invention;

FIG. 2 is a simplified schematic of circuitry according to an embodimentof the present invention;

FIG. 3 illustrates a state diagram for a system management controlleraccording to an embodiment of the present invention;

FIG. 4 illustrates various states of an adapter state machine accordingto an embodiment of the present invention;

FIG. 5 is a state diagram for fault detection circuitry according to anembodiment of the present invention;

FIG. 6 illustrates a state diagram for detecting a connection between apower adapter and an electronic device according to an embodiment of thepresent invention;

FIG. 7 illustrates circuitry for detecting a connection between a poweradapter and an electronic device according to an embodiment of thepresent invention;

FIG. 8 illustrates a state diagram for providing power from a poweradapter to an electronic device according to an embodiment of thepresent invention;

FIG. 9 illustrates circuitry for providing power from a power adapter toan electronic device according to an embodiment of the presentinvention;

FIG. 10 illustrates state diagrams for transmitting data between anadapter and an electronic device according to an embodiment of thepresent invention;

FIG. 11 illustrates circuitry for transmitting data according to anembodiment of the present invention;

FIG. 12 is a schematic of a driver circuit according to an embodiment ofthe present invention;

FIG. 13 illustrates circuitry for a power adapter according to anembodiment of the present invention;

FIG. 14 illustrates a driver circuit according to an embodiment of thepresent invention;

FIG. 15 illustrates a finite-state machine according to an embodiment ofthe present invention;

FIG. 16 illustrates another detection circuit according to an embodimentof the present invention;

FIG. 17 illustrates a power adapter and an electronic device connectedthrough a converter according to an embodiment of the present invention;

FIG. 18 illustrates circuitry for a converter or connector adapteraccording to an embodiment of the present invention;

FIG. 19 illustrates circuitry for a converter or connector adapteraccording to an embodiment of the present invention;

FIG. 20 illustrates a circuit that may be used for connection detectionaccording to an embodiment of the present invention; and

FIG. 21 illustrates another circuit that may be used for connectiondetection according to an embodiment of the present invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 illustrates an electronic system that may be improved by theincorporation of embodiments of the present invention. This figure, aswith the other included figures, is shown for illustrative purposes anddoes not limit either the possible embodiments of the present inventionor the claims.

This figure includes electronic device 110. In this specific example,electronic device 110 may be a laptop computer. In other embodiments ofthe present invention, electronic device 110 may be a netbook or tabletcomputer, cell, media, or smart phone, global positioning device, mediaplayer, or other such device.

Electronic device 110 may include a battery. The battery may providepower to electronic circuits in electronic device 110. This battery maybe charged using power adapter 120. Specifically, power adapter 120 mayreceive power from an external source, such as a wall outlet or carcharger. Power adapter 120 may convert received external power, whichmay be AC or DC power, to DC power, and it may provide the converted DCpower over cable 130 to plug 132. Plug 132 may be arranged to mate withreceptacle 112 on electronic device 110. Power may be received atreceptacle 112 from plug 132 and provided to the battery and electroniccircuitry in electronic device 110.

Again, it may be desirable for electronic device 110 to be able tocontrol the power received from power adapter 120. For example,electronic device 110 may monitor a temperature of power adapter 120. Inthis way, the electronic device may adjust the power drawn from poweradapter 120 such that the temperature of power adapter 120 is held belowa certain level. This may allow the use of a smaller, less expensive,power adapter 120. Also, on occasion, it may be more power efficient forelectronic device 110 to draw power from its battery rather than frompower adapter 120. When this occurs, electronic device 110 may turn offpower adapter 120 and draw power from its battery instead.

In other embodiments of the present invention, other parameters may becontrolled, monitored, or otherwise measured. For example, in a solarcell system, a maximum power point may be tracked. In other embodimentsof the present invention, an electronic device may be able to give anadvance warning to the adapter of an upcoming event. For example, anelectronic device may be able to warn an adapter that a battery is aboutto be charged. This information may be used to control various supplyand protection circuits in the power adapter, or for other purposes.This may allow the power adapter to be able to prepare itself todelivery the power in a more efficient manner. This may be of particularimportance in fuel cell systems, for example, since the fuel cell mayneed a lot of time to build pressure in its conversion chamber. That is,embodiments of the present invention may be able to give a fuel cellsystem a prior warning of battery charging current using thiscommunication path. Such an advance warning may be important in makingthis alternative fuel system practical.

Also, in various embodiments of the present invention, plug 132 mayinclude an LED 134. LED 134 may be used to indicate a power connectionbetween power adapter 120 and electronic device 110. Accordingly, whenpower adapter 120 detects a connection to electronic device 110, poweradapter 120 may activate LED 134.

Accordingly, embodiments of the present invention may providecommunications between power adapter 120 and electronic device 110.Embodiments of the present invention may further provide communicationsbetween power adapter 120 and circuitry associated with LED 134. In thisway, electronic device 110 may read data from power adapter 120, andinstruct power adapter 120 to adjust its current or turn off. Similarly,power adapter 120 may communicate with circuitry associated with LED134, instructing LED 134 to turn off or on as needed.

Again, it may be desirable for power adapter 120 to be able to provide amaximum amount of power over cable 130 to electronic device 110.Accordingly, embodiments of the present invention provide circuitry suchthat these communications may occur over power conductors in cable 130.Since no additional wires are needed for this communication, all of thewire in cable 130 may be available to deliver power to electronic device110. An example of this circuitry is shown in the following figure.

FIG. 2 is a simplified schematic of circuitry according to an embodimentof the present invention. This circuitry may include circuitry in apower adapter, power plug, and electronic device or system. Thiscircuitry may include circuitry for three main functions. The firstcircuitry may include detection circuitry to detect the presence of aconnection between a power adapter and an electronic device. The secondcircuitry may include power circuitry for delivering power from thepower adapter to the electronic device. The third circuitry may includecircuitry for a first signal path between the power adapter to the powerplug and a second signal path between the power adapter and theelectronic device. This circuitry is explained further in the figuresbelow.

This circuitry may include a system management controller (SMC) in thesystem or electronic device, and an adapter microcontroller in the poweradapter. These controllers may control states of the power adapter andthe power circuitry in the electronic device. An example of statediagrams that may be used by embodiments of the present invention isshown in the following figures.

FIG. 3 illustrates a state diagram for a system management controlleraccording to an embodiment of the present invention. Upon power up ofthe electronic device, state 310 may be entered. Once power is receivedfrom the power adapter, the presence of a valid power adapter may bedetected in state 320.

In this state, power is received by the electronic device from the poweradapter, and one of two things may happen, either the power may beremoved, or the electronic device may wish to initiate communications.(In a specific embodiment of the present invention, only the electronicdevice can initiate communications, since such communications requirethe power adapter to turn off the power supplied to the electronicdevice, and the absence of such power may cause the electronic device toturn off when battery charge is low.) If power is disconnected, a resetsignal may be issued in state 340, essentially inquiring whether thepower adapter has been disconnected. If the power adapter has beendisconnected, no response will be received, and the state machine mayreturn the state 310. When the electronic device intends to initiatecommunications with a power adapter, state 330 is entered, and the resetsignal is issued in state 340. If a return signal is observed, the linkactive state can be entered in state 350. In this case, data may betransferred. Once data has been transferred, an end bit in state 360 maybe sent. This end bit may instruct all of the previous commands to beexecuted, though in other embodiments of the present invention, commandsare executed as they are received. In state 370, the electronic devicemay wait for a response from the power adapter. If no response isreceived, the electronic device may enter state 310. If a response isreceived, the electronic device may continue to receive power in state320.

FIG. 4 illustrates various states of an adapter state machine accordingto an embodiment of the present invention. Upon power up of the adapter,the adapter may enter a sleep mode in state 410. Once a connection to anelectronic device is detected, state 420 may be entered. If thisdetection is stable and below specific current levels, state 440 may beentered. Once a reset pulse is observed, a response signal may beprovided in state 450. Link active state 460 may be entered once thepresent signal has been sent. In this state, signals may be provided andreceived. After an end bit is received from the electronic device, thepower adapter may enter state 430 and continue providing power to theelectronic device.

In various embodiments of the present invention, under-voltage orover-current conditions may be detected. In such cases, power to theadapter may be cycled, thereby restarting or resetting the poweradapter. An example is shown in the following figure.

FIG. 5 is a state diagram for fault detection circuitry according to anembodiment of the present invention. When an under-voltage occurs, state510 may be entered. When over-current condition occurs, state 520 may beentered. After either of these states is entered, the power to theadapter may be cycled, thereby resetting the adapter.

Again, in a specific embodiment of the present invention, when a poweradapter is initially connected to an electronic device, that connectionis detected by the power adapter. An example of the state diagrams andcircuitry involved is shown in the following figures.

FIG. 6 illustrates a state diagram for detecting a connection between apower adapter and an electronic device according to an embodiment of thepresent invention. Upon power up, the power adapter may enter stage 610.After a detection, the power adapter may enter stage 620. Power may beenabled and provided to the electronic device in state 630.

Upon power up, the electronic device may enter state 640. Once theelectronic device senses that power is being provided, the electronicdevice may recognize that a valid adapter is present and enter state650.

FIG. 7 illustrates circuitry for detecting a connection between a poweradapter and an electronic device according to an embodiment of thepresent invention. When a connection between a power adapter andelectronic device or system is made, wire 700 is coupled to groundthrough resistor Rsys. The resulting low voltage may be detected bycomparator C2, which may provide a detect signal to the power adaptercircuitry. This may indicate to the power adapter that a connection hasbeen made and power may be supplied. In various embodiments of thepresent invention, Rsys is chosen such that a stray or “organic”resistance (such as a user's finger) likely has a different value. Thishelps to prevent mistaken connection detections by the power adapter.

Specifically, power supply 710 may include an LDO, which provides avoltage to resistor Rldo. This voltage may generate a current throughRldo, D1, and Rsys. Again, the resulting voltage may be detected bycomparator C2, which may provide a detect signal back to the poweradapter. In a specific embodiment of the present invention, comparatorC5 is not switched by this event. Rather, comparator C5 is switched whenfull power is provided by the power adapter to the electronic device.Rsys may have various values, depending on device type. In this way, thedevice type being charged by the power adapter can be identified by thepower adapter.

In this example, terminals of the power plug may see a large resistancein series with a low-voltage supply. This configuration may limit thecurrent that may be drawn from the power adapter when a valid connectionis not detected. In this way, when contacts on the power plug aretouched by a user, significant current may not be drawn from the poweradapter.

Again, once a valid connection is detected by the power adapter, powermay be provided to the electronic device. Once power is received by theelectronic device, one of two things may happen, either the power maybecome disconnected, or the electronic device may wish to initiatecommunications. Examples of a state diagram and associated circuitry areshown in the following figure.

FIG. 8 illustrates a state diagram for providing power from a poweradapter to an electronic device according to an embodiment of thepresent invention. Again, the power adapter may be in state 810, andthereby providing power to an electronic device. The power adapter mayreceive a signal from the electronic device initiating communications,and thereby entering state 820.

Similarly, the electronic device may receive power in state 830. Powermay then be disconnected, whereupon the electronic device may issue areset signal in state 850. Alternately, the electronic device mayinitiate communications and enter state 840. Again, a reset signal maybe issued in state 850.

FIG. 9 illustrates circuitry for providing power from a power adapter toan electronic device according to an embodiment of the presentinvention. In this example, power supply 710 is provided via power wires700 to the electronic device. This power may be received by charger 900.Charger 900 may provide power to a battery or other circuitry in theelectronic device or system.

On occasion a system may enter a low-power state, such as sleep or off.In these circumstances, power may be periodically connected to anddisconnected from the load by turning transistor MPOWER on and off. Theperiod and duty cycle of this may be varied, depending on the powerdrawn by the system in the lower-power state. In a specific embodiment,in an off state, a duty cycle may be 300:1 (off-to-on ratio), while in asleep state the ratio may be approximately 30:1.

Again, when a valid connection between the power adapter and electronicdevice is detected, it may be desirable to activate an LED on the powerplug to indicate this. Accordingly, an LED may be provided in a powerplug. In this example, the LED is driven by a current source controlledby a programmable switch. This programmable switch may be a programmableI/O circuit, such as the DS2413 provided by Maxim Integrated Products ofSunnyvale, Calif., though in other embodiments of the present invention,other switches may be used. Again, once a connection is detected, thepower adapter may instruct the programmable switch to turn on the LED,thereby indicating the presence of a connection between the poweradapter and the electronic device or system.

Under some conditions, a user may later turn off the system. At thattime, the system may instruct the programmable switch to turn off theLED. Under other conditions, however, the power adapter may experiencean asynchronous disconnect. That is, a user may simply pull the plugfrom the system. In this case, the power adapter may turn off the powerFET MPOWER, which may shut off the LED.

Again, wires 700 may be used to transmit data. Examples of statediagrams and associated circuitry are shown the following figures.

FIG. 10 illustrates state diagrams for transmitting data between anadapter and an electronic device according to an embodiment of thepresent invention. Initially, the power adapter may be enabled in state1005. If current drops below a set level, the power adapter mayunderstand that the electronic device may initiate communications.Following a response signal provided by the power adapter in state 1015,the power adapter may enter the link active states 1020. In this state,signals may be provided and received. After an end bit is received fromthe electronic device, the power adapter may enter state 430 andcontinue providing power to the electronic device.

Upon power up of the electronic device, state 1050 may be entered. Oncepower is received from the power adapter, the presence of a valid poweradapter may be detected in state 1055. In this state, power may bereceived by the electronic device from the power adapter, and one of twothings may happen, either the power may be removed, or the electronicdevice may wish to initiate communications. If power is disconnected, areset signal may be issued in state 1065, essentially inquiring whetherthe power adapter has been disconnected. If the powered adapter has beendisconnected, no response will be received, and the state machine mayreturn the state 1050.

When the electronic device intends to initiate communications with apower adapter, state 1060 is entered, and the reset signal is issued instate 1065. If a return signal is observed, the link active state can beentered in state 1070. In this case, data may be transferred. Once datahas been transferred, an end bit in state 1075 may be sent. This end bitmay instruct all of the previous commands to be executed, though inother embodiments of the present invention, commands are executed asthey are received. In state 1080, the electronic device may wait for aresponse from the power adapter. If no response is received, theelectronic device may enter state 1050. If a response is received, theelectronic device may continue to receive power in state 1055, and powermay be provided from the power adapter to the electronic device.

Again, temperature data may be transmitted from the power adapter to thesystem. The system can use this data to monitor the power adapter andprevent overheating. In other embodiments of the present invention,other types of data may be transmitted between the power adapter andsystem. For example, identification data that includes current andvoltage capabilities, adapter identification, and version informationmay be transmitted. Still other embodiments of the present invention mayinclude fault logging. Faults, such as overheating, overvoltage, or overcurrent faults, may be transmitted or stored by either or both theelectronic device and the power adapter. For example, if a power adapterwere to shut down due to overheating, it could record that data in a logfor later retrieval. Also, this data could be transmitted by the poweradapter to the system for diagnosis by the system.

FIG. 11 illustrates circuitry for transmitting data according to anembodiment of the present invention. Drive circuitry for sending andreceiving data may be included in both the power adapter and system.Also, a current path to maintain the LED in an illuminated state duringdata transmission may be provided. In this specific example, an LDOprovides a current through a 500 ohm resistor to the LED. An example ofthe drive circuitry that may be used in the power adapter and electronicdevice is shown in the following figure.

FIG. 12 is a schematic of a driver circuit according to an embodiment ofthe present invention. In various embodiments of the present invention,this driver circuit may provide at least three functions. It may providea low leakage path during connection detection, it may protect amicrocontroller or other circuitry from high voltage during powertransmission, and it may provide a strong pull-down during datatransmission.

This drive circuitry may include transistor M1. Transistor M1 may beused to provide a high impedance for the drive circuitry when aconnection is being detected. Transistors M2 may be provided to isolatemicrocontroller power supply V1 from high voltages provided on wires 700during power transmission. During signaling, a low signal may beprovided by transistor Q1. Specifically, transistor Q1 may turn on andpull wire 700 low. Resistor R1 may be included as a pull up to provide ahigh signal level on wire 700.

In various embodiments of the present invention, other circuitry may beused consistent with embodiments of the present invention. Examples areshown in the following figures.

FIG. 13 illustrates circuitry for a power adapter according to anembodiment of the present invention. As before, this circuitry mayinclude circuitry for at least three functions. Specifically, thiscircuitry may include circuitry to detect a connection to an electronicdevice, circuitry to transmit power to the electronic device, andcircuitry to communicate with other circuitry, such as circuitry in apower plug or the electronic device.

In this specific example, detection circuitry is included. Specificallylow dropout (LDO) regulator U2 may provide a low voltage to a terminalof resistor R4. This low voltage may be provided through resistor R4 anddiode D2 to line VO 700, which may be a power conductor. Again, this mayprovide a fairly high impedance at terminals of a power plug, therebyprotecting users from accidental exposure to potentially dangerouscurrents and voltages.

As before, a pull down resistor Rsys may reside in the electronicdevice. When Rsys is connected to line VO 700, the voltage on VO drops.This drop in voltage can be detected by comparator U3, which may providea system detected signal. In other embodiments of the present invention,circuitry for U3 may be more sophisticated and may be able to detectvarious voltages on line VO. These various voltages may indicate variousresistances for Rsys, thereby indicating a type of device being charged.

Also, in this specific embodiment of the present invention, powercircuitry may be included to provide power from the power adapter to theelectronic device. Specifically, a power supply is connected to terminalV+. Connector M1 may be enabled, thereby connecting line VO 700 to thepower supply V+.

Also in this specific embodiment of the present invention, communicationcircuitry may be included. This circuitry may allow the power adapter tocommunicate with the electronic device, circuitry in a power plug, orother circuitry. This circuitry may include a low dropout regular U1.Low dropout regulator U1 may connect in series through resistor R1 anddiode D1. This configuration may be used to ensure that an LED in thepower plug remains illuminated during data communications.

The data communications may be achieved using a one-wire driver X1. Anexample of such a driver is shown in the following figure.

FIG. 14 illustrates a driver circuit according to an embodiment of thepresent invention. Driver 1400 may communicate with an electroniccircuit and circuitry in a power plug over wire via 700. As before, thisdriver may provide at least three functions.

First, during a detection, a high impedance may be provided such thatthe detection circuitry may operate properly. Specifically, Zener diodeD1 is off at low voltages, such as the low voltage provided by U2 duringdetection, and therefore provides a high impedance during detection.

Second, during power transmission, protection from the high voltages isprovided to the microcontroller circuitry. Again, Zener diode D1 stepsoff a significant portion of the high-voltage, while the resistordivider formed by resistors R1 and R2 divides down the remainingvoltage.

Third, logic levels are provided on line VO 700. Specifically,transistor Q1 may pull down on line 700, while resistor Rp may provide apull-up on line 700.

Data may be received by this circuit through diode D1 by buffer B. Thebuffer B may drive a finite-state machine, which in turn may drivebuffer C. Buffer C may drive transistor M1, which in turn drives outputline IO.

Data may be driven by this circuit by driving line IO, and therebydriving buffer A. Buffer A may drive the finite-state machine, which inturn may drive buffer B. Buffer B may drive transistor Q1, which maydrive line VO 700.

In various embodiments of the present invention, a state machine may beused to resolve conflicts between the incoming and outgoing data paths.For example, in various configurations, without a finite state machine,the four buffers (or comparators) and associated transistors may latchinto a stable state. In other configurations, without the finite-statemachine, the four buffers and associated transistors may oscillate.Accordingly, to resolve these conflicts, a finite-state machine may beused. An example of such a state machine is shown in the followingfigure.

FIG. 15 illustrates a finite-state machine according to an embodiment ofthe present invention. This state machine may be asynchronous, that is,it is not clocked. In other embodiments of the present invention, thisstate machine may be clocked.

In this example, eight total states are mapped by the look-up table1500. State diagram 1510 illustrates various states of the finite-statemachine. For example, if the present state is S0, and the inputs A and Bchange to a zero and a one respectively, the finite state machine maymove to state S3.

Two additional or unused states U0 and U1 unconditionally move to knownthe states S3 and S4 in order to avoid a stable condition in the eventthat one of these states is accidentally entered. Such an accidentalentry may be caused by power glitches or other transitory conditions.

Again, the detection circuitry shown in FIG. 7 may be used to identify avalue of a system identification resistor in an electronic device orsystem. This value may then be used to verify that a valid connectionbetween a power adapter and electronic device has been made. In otherembodiments of the present invention, other information about theelectronic device may be determined from the value of the systemresistor. For example, a current receiving capability, device type, orother information about the electronic device may be indicated by thevalue of the system resistor.

Unfortunately, various factors, such as leakage currents, diode voltagedrops, and other error terms, may reduce the accuracy of thismeasurement. In order to improve such measurements, a differentialvoltage may be detected. That is, two detection measurements may bemade. These measurements may be subtracted from each other or otherwiseused to more accurately measure the system resistor. An example is shownin the following figure.

FIG. 16 illustrates another detection circuit according to an embodimentof the present invention. This detection circuitry includes detectioncircuitry in a power adapter and in an electronic device or system.

As before, a low dropout regulator may provide a voltage through aresistor RS1 in the power adapter to a system resistor Rsys, located inthe electronic device or system. When a valid connection is made betweenthe power adapter and the electronic device, a resulting voltage may bedetected by an analog-to-digital converter.

In this example, a second measurement may be made by connecting a secondresistor RS2 in parallel with resistor RS1. Specifically, a switch,shown here as a p-channel field-effect transistor, may be closed,thereby shorting resistor RS2 across resistor RS1. The field-effecttransistor may be in a first state (for example, off) until a voltage ina first range is detected by the analog-to-digital converter. Once sucha voltage is detected, control circuitry may change the state of thefield-effect transistor (for example, to on), and a second voltage maybe detected.

This change in impedance in series with the low dropout regulator mayresult in a change in a voltage detected by the analog-to-digitalconverter. These two detected voltages may be subtracted from each otherto generate a differential voltage. This differential voltage may thenbe used to determine the value of the system resistor. Using such adifferential measurement may reduce the effects of various leakagecurrents, diode drops, ground drops, and other error terms. Whilevarious nonlinear errors, such as nonlinearities associated with thediode, may largely remain, the accuracy of the measurement may beincreased by using such a differential measurement.

While in this embodiment of the present invention a differentialmeasurement is made by switching a second resistor in parallel with afirst resistor, in other embodiments of the present invention, othercircuit techniques may be used. For example, a voltage provided by thelow dropout regulator may be varied. In other embodiments of the presentinvention, a second resistor in series with the first resistor may beswitched in and out and a differential measurement may be made.

On occasion, it may be desirable to connect a power adapter to anelectronic device or system, where the power adapter and electronicdevice are not compatible. For example, a power adapter may have aconnector insert that has a first form factor, while the electronicdevice may have a receptacle for receiving connector inserts having asecond form factor. Accordingly, embodiments of the present inventionprovide a connector adapter or converter that allows for such aconnection to be made. For example, the converter may have a receptaclethat accepts connector inserts having a first form factor. The convertermay also have a connector insert having the second form factor, suchthat the converter may be inserted into the electronic device or system.An example of a system including such as converter is shown in thefollowing figure.

FIG. 17 illustrates a power adapter and an electronic device connectedthrough a converter according to an embodiment of the present invention.This converter may include a converter resister that may be detected bya power adapter. More specifically, the series combination of theconverter resister RCNV and the system resistor RSYS may be detected bythe power adapter. This may inform the power adapter that a legacy (orother) device is being powered through a converter or connector adapter.Once power is to be applied to the system, the converter resister RCNVmay be removed from the power path to avoid the power dissipation thatwould otherwise result. This may be done using a switch. An example ofsuch a configuration is shown in the following figure.

FIG. 18 illustrates circuitry for a converter or connector adapteraccording to an embodiment of the present invention. In this example, aninput terminal IN may be connected to a pin of a connector receptacle onthe converter that accepts a connector insert that is coupled to a poweradapter, while an output terminal OUT may be coupled to a pin of aconnector insert that may mate with a connector receptacle housed in anelectronic device.

This circuitry includes a detection resistor R3 in parallel with switchM1. During detection, the voltage received on line IN is low and switchM1 is off, and therefore resistor R3 may be detected by circuitry in thepower adapter.

Once the presence of a valid connection has been determined, a voltageon line IN may rise. This increased voltage may result in a currentthrough resistor R2, which may provide a gate-to-source voltage fortransistor M1. This, in turn, may turn transistor M1 on, therebyshorting resistor R3 and allowing power to flow from the input terminalIN to the output terminal OUT.

In various embodiments of the present invention, additional circuitry,such as overvoltage protection, may be included in a converter accordingto an embodiment of the present invention. An example is shown in thefollowing figure.

FIG. 19 illustrates circuitry for a converter or connector adapteraccording to an embodiment of the present invention. This circuitryincludes overvoltage circuitry connected to terminal IN. In summary, inovervoltage conditions, this circuitry turns on transistor Q1, therebyshorting resistor R2 and turning off transistor switch M1. This, inturn, places resistor R3 in series with the electronic device, therebyprotecting the electronic device from the overvoltage condition.

In various embodiments of the present invention, a system resistor maybe used to indicate the presence of a connection of an electronic deviceto a power adapter. Again, other information about the electronic devicemay be conveyed by a value of this resistor. In other embodiments of thepresent invention, other circuits may be used for this detection andidentification. Examples are shown in the following figures.

FIG. 20 illustrates a circuit that may be used for connection detectionaccording to an embodiment of the present invention. This circuitryincludes a first system resistor RSYS1 in parallel with a seriescombination of a diode RSYS DIODE and second system resistor RSYS2. Whena low voltage is received on line IN, the diode may be off, and the loadon line IN may be approximately the first system resistor RSYS1. As thevoltage on line IN is increased, the load may change to a parallelcombination of the first and second system resistors.

This two-step procedure may be used in various ways. For example, such aprocedure may be much less likely to result in a mistaken connectiondetection. That is, while a stray impedance may lead a power adapter toincorrectly determine that a connection to an electronic device has beenmade, such an error is much less likely in such a dual impedancemeasurement. In other embodiments of the present invention, a firstmeasurement may be used to determine the presence of a connection, whilea second measurement may be used to convey information about theelectronic device such as charging capability, device typeidentification, or other information.

FIG. 21 illustrates another circuit that may be used for connectiondetection according to an embodiment of the present invention. Thiscircuitry includes a system resistor RSYS 1 in parallel with a diodeRSYS DIODE. When a high voltage is received, the diode may clamp theinput line IN. As this voltage is decreased, the load may appear to beequal to the system resistor RSYS. As before, this two-step process ismuch like is likely to result in an incorrect connection determinationby a power adapter. Also, the clamp voltage or value of the systemresistor, or both, may be used to convey information about theelectronic device.

The above description of embodiments of the invention has been presentedfor the purposes of illustration and description. It is not intended tobe exhaustive or to limit the invention to the precise form described,and many modifications and variations are possible in light of theteaching above. The embodiments were chosen and described in order tobest explain the principles of the invention and its practicalapplications to thereby enable others skilled in the art to best utilizethe invention in various embodiments and with various modifications asare suited to the particular use contemplated. Thus, it will beappreciated that the invention is intended to cover all modificationsand equivalents within the scope of the following claims.

What is claimed is:
 1. A method of operating an electronic device, the method comprising: detecting a connection of a power adapter at a receptacle of the electronic device; drawing power from the power adapter at the electronic device receptacle; determining that power would be more efficiently provided by a battery internal to the electronic device; instructing the power adapter to not provide power to the electronic device receptacle; and drawing power from the battery.
 2. The method of claim 1 wherein detecting a connection of a power adapter at a receptacle comprises receiving a voltage at a first network from a power conductor, then comparing a resulting voltage on the power conductor to a threshold voltage.
 3. The method of claim 2 wherein the first network comprises a resistor.
 4. The method of claim 2 wherein the first network comprises a first resistor in parallel with a series combination of a second resistor and a diode.
 5. The method of claim 2 wherein the first network comprises a resistor in parallel with a diode.
 6. The method of claim 1 wherein the battery is a fuel-cell battery.
 7. The method of claim 6 wherein the electronic device is a fuel-cell system.
 8. A method of operating an electronic device, the method comprising: detecting a connection of a power adapter at a receptacle of the electronic device; drawing a first level of power from the power adapter over a first power conductor; requesting temperature data from the power adapter over the first power conductor; receiving temperature data from the power adapter over the first power conductor; and drawing a second level of power from the power adapter over the first conductor, wherein the change in drawn power from the first level to the second level is based on the temperature data.
 9. The method of claim 8 further comprising before requesting temperature data from the power adapter, not drawing the first level of power from the power adapter.
 10. The method of claim 9 wherein in response to the electronic device not drawing the first level of power from the power adapter, the power adapter does not provide a supply voltage to the receptacle of the electronic device over the first power conductor.
 11. The method of claim 9 wherein the second level of power is determined in order to keep a temperature of the power adapter below a first temperature.
 12. The method of claim 9 wherein detecting a connection of a power adapter at a receptacle comprises receiving a voltage at a first network from a power conductor, then comparing a resulting voltage on the power conductor to a threshold voltage.
 13. The method of claim 8 wherein the first network comprises a resistor.
 14. The method of claim 8 wherein the electronic device is a fuel-cell system.
 15. A method of operating an electronic device, the method comprising: detecting a connection of a power adapter at a receptacle of the electronic device; drawing a first level of power from the power adapter over a first conductor; reducing the level of power from drawn from the power adapter to a second level over the first conductor; sending a first signal to the power adapter over the first conductor; and resuming drawing the first level of power from the power adapter over the first conductor.
 16. The method of claim 15 further comprising after sending a first signal to the power adapter over the first conductor, receiving a second signal from the power adapter over the first conductor.
 17. The method of claim 15 wherein the first signal is a request for temperature data from the power adapter.
 18. The method of claim 15 wherein the first signal is a request for identification information from the power adapter.
 19. The method of claim 15 further comprising charging a battery in the electronic device.
 20. The method of claim 19 wherein the battery is a fuel-cell battery. 